Polyurethane

ABSTRACT

A polyurethane comprises (a) organic diisocyanate units and (b) polycaprolactone polyol units having a narrow molecular weight distribution in which a ratio of the weight average molecular weight to the number average molecular weight is in the range of from 1.1 to 2.0 and the average molecular weight is 500 to 5,000, the units (a) and (b) being connected linearly through urethane linkages.

The present invention relates to a lactone polymer, especially a lactonepolymer having a narrow molecular weight distribution, and a process forthe preparation thereof. Moreover, the invention relates to apolyurethane and a process for the preparation thereof. Moreparticularly, the invention relates to a polyurethane which is excellentin the elastic recovery and has a very good operation adaptabilitybecause of a low viscosity thereof and a process for the preparationthereof. The polyurethane is obtained from diisocyanate and the beforementioned lactone polymer. The lactone polymer having a molecular weightof 500 to 5,000 is very valuable as a starting material to be used formanufacture of polyurethanes, paints and the like.

Conventional lactone polymers having a molecular weight of 500 to 5,000,however, have a broad molecular weight distribution and the ratio of theweight average molecular weight to the number average molecular weightis in the range of from 2.5 to 3.5. When such polymers are actuallyused, various problems are caused by this broad molecular weightdistribution.

We made researches on molecular weight distributions of conventionallactone polymers by gel permeation chromatography (hereinafter referredto as "GPC"), and found that if the molecular weight distribution isappropriately adjusted, lactone polymers giving practically veryexcellent characteristics can be obtained. We have now completed thepresent invention based on this finding.

More specifically, in accordance with the present invention, there areprovided a lactone polymer having a narrow molecular weightdistribution, which is characterized in that the ratio of the weightaverage molecular weight to the number average molecular weight is inthe range of from 1.1 to 2.0 and the molecular weight is 500 to 5,000,and a process for the preparation of such lactone polymer.

By the term "lactone polymer" used in the present invention is meant apolymer obtained by subjecting ε-caprolactone to ring-openingpolymerization in the presence of an initiator containing an activehydrogen atom. As the initiator, there can be used polyhydric alcoholssuch as diols and triols and polyvalent amines. As the diol, there canbe mentioned ethylene glycol, propylene glycol, diethylene glycol,1,4-butylene glycol, 1,6-hexane diol and neopentyl glycol. As the triol,there can be listed glycerin and trimethylol-propane. Other polyhydricalcohols include pentaerythritol, acrylic polyols, styrene/allyl alcoholcopolymers and polymeric resins having hydroxyl groups such aspolyester-polyols, epoxy resins, polyether polyols and cellulosederivatives. The polyvalent amine include ethylene diamine, diethylenetriamine and ethanol amine. Moreover aromatic polyamines may be usedhere.

By the term "molecular weight" used in the present invention is meant avalue calculated from the hydroxyl value of the lactone polymeraccording to the following formula: ##EQU1##

The hydroxyl value is determined according to the method of JIS K-15576.4. In the above formula, N represents the number of functional groupsof the initiator.

The molecular weight of the lactone polymer of the present invention is500 to 5,000.

As is apparent from the foregoing description, the amount of thepolymerization initiator necessary for obtaining a predeterminedmolecular weight can be defined according to the above calculationformula.

The ratio of the weight-average molecular weight Mw to thenumber-average molecular weight Mn, that is, the molecular weightdistribution, is determined by GPC.

Apparatus:

Model LC-3A manufactured by Shimazu Seisakusho

Solvent:

tetrahydrofuran, 1 ml/min

Temperature:

room temperature

Columns:

HSG-PRE (one), HSG-20 (one), HSG-15 (three) and HSG-10 (one)

(each being supplied by Shimazu Seisakusho)

Detector:

Shodex RI SE-11 (supplied by Showa Denko)

The ratio of the weight average molecular weight to the number averagemolecular weight is in the range of from 1.1 to 2.0.

The process for the preparation of the polymer of the present inventionwill now be described.

In the preparation process according to the present invention, astannous halide such as stannous chloride, stannous bromide or stannousiodide is used as a catalyst. The amount used of the catalyst is 0.1 to50 ppm based on the total weight of ε-caprolactone. If the amount usedof the catalyst is smaller than 0.1 ppm, polymerization is not advanced,and if the amount used of the catalyst is larger than 50 ppm, it becomesdifficult to obtain a polymer having a narrow molecular weight. Thereaction temperature is ordinarily 100° to 230° C. and preferably 120°to 190° C.

Since a known catalyst, TBT (tetrabutyl titanate), contributes not onlyto ring-opening polymerization but also to ester exchange reaction, useof this catalyst results in production of a polymer having a broadmolecular weight distribution.

The lactone polymer of the present invention has a narrower molecularweight distribution than the conventional lactone polymer and also has alower viscosity and a slightly lower melting point than those of theconventional polymer.

Since the molecular distribution of the lactone polymer of the presentinvention is narrow, it is very valuable as a starting material to beused for manufacture of urethane elastomers, urethane adhesives,urethane paints and polyurethanes.

For example, when the polymer of the present invention is used in thefield of spandex fibers, there can be provided products excellent in theelastic recovery characteristics. Furthermore, there can be provided ahigh-solid paint as a polyol component of a two-pack type urethanepaint.

Polyurethanes having a linear structure have heretofore been synthesizedby reacting a polyol having hydroxyl groups on both the molecule ends,an organic diisocyanate and a chain extender having a relatively lowmolecular weight such as a diol or diamine. As the polyol havinghydroxyl groups on both the molecule ends, there are used polyester typepolyols and polyether type polyols. As the polyester type polyol, thereare ordinarily used a polyester polyol synthesized from ethylene glycolor 1,4-butylene glycol and adipic acid and a polycaprolactone polyolprepared from ε-caprolactone. The conventional polycaprolactone polyolis defective in that it is inferior to polyether type polyols,especially polytetramethylene glycol (PTMG), in the elastic recovery.Accordingly, the conventional polycaprolactone polyol cannot be used inthe fields where a high elastic recovery is required. When polyestertype polyols are used for the synthesis of urethane prepolymers to beused for casting or urethane type adhesives, their operationadaptability is bad because of a high viscosity, and if the viscosity isreduced so as to improve the operation adaptability, the characteristicsof the resulting polyurethanes are degraded.

We made researches with a view to eliminating these defects ofconventional polycaprolactone type polyurethanes, and we found that apolyurethane prepared by using a polycaprolactone polyol having a narrowmolecular weight distribution has an excellent elastic recovery notobserved in the conventional products and it has a lower viscosity thanthose of the conventional products and a highly improved operationadaptability in the synthesis of prepolymers and urethane typeadhesives. We have now completed the present invention based on thisfinding.

More specifically, the present invention relates a polyurethane preparedby reacting an organic diisocyanate with a compound containing at leasttwo active hydrogen atoms in the molecule, wherein a polycaprolactonepolyol having a narrow molecular weight distribution in which the ratioof the weight average molecular weight to the number average molecularweight is in the range of from 1.1 to 2.0 and the average molecularweight is 500 to 5,000, is used as the active hydrogen atom-containingcompound, and a process for the preparation thereof.

As the organic diisocyanate that is used in the present invention, therecan be mentioned, for example, 2,4-tolylene diisocyanate, 2,6-tolylenediisocyanate, 4,4'-diphenylmethane diisocyanate, tolidine diisocyanate,hexamethylene diisocyanate, isophorone diisocyanate and 1,5-naphthalenediisocyanate. As the chain extender that is used in carrying out thepresent invention, there are preferably used ethylene glycol, propyleneglycol, 1,4-butylene glycol and 1,6-hexamethylene diol. Furthermore,there can be used ethylene diamine, propylene diamine and hydrazine.

For preparing the polyurethane of the present invention, there ispreferably adopted a prepolymer process comprising reacting a polyolwith an excessive amount of an organic isocyanate to form anisocyanate-terminated prepolymer and then reacting the formed prepolymerwith a chain extender such as a diol or diamine. As the solvent to beused for the preparation of a solution type polyurethane, such as aurethane adhesive, there can be used ordinary solvents such as toluene,ethyl acetate, methylethyl ketone and dimethylformamide.

The polycaprolactone type polyurethane of the present invention isexcellent over the conventional products in the elastic recovery and hasa low viscosity and a good operation adaptability. This is due to thefact that the molecular distribution of the polycaprolactone polyol isnarrow and in the range of from 1.1 to 2.0.

The polyurethane of the present invention can be used veryadvantageously for manufacture of a spandex products, adhesives,artificial leathers and paints.

The present invention will now be described in detail with reference tothe following Examples and Comparative Examples that by no means limitthe scope of the invention. In these Examples, all of "parts" are byweight.

EXAMPLES 1 THROUGH 4 AND COMPARATIVE EXAMPLES 1 THROUGH 3 [PolymerHaving Molecular Weight of 2000]

A three-neck separable flask having a capacity of 1 liter was chargedwith 969 g (8.5 moles) of ε-caprolactone, 31 g (0.5 mole) of ethyleneglycol and a predetermined amount of a catalyst. A thermometer, acondenser and a nitrogen-introducing tube were attached to the flask,and reaction was carried out at a predetermined temperature in anitrogen gas atmosphere. When the content of ε-caprolactone measured bygas chromatography was lower than 0.5%, the reaction was stopped, andthe reaction product was cooled and withdrawn.

EXAMPLE 5 AND COMPARATIVE EXAMPLE 4 [Polymer Having Molecular Weight of1250]

Procedures of the foregoing Examples were repeated in the same mannerexcept that 594 g (5.2 moles) of ε-caprolactone and 31 g (0.5 mole) ofethylene glycol were charged.

                                      TABLE 1                                     __________________________________________________________________________                 Reaction Conditions                                                     Molecular                                                                           Catalyst                                                                           Temper-                                                                             Time     Melting                                                                             Viscosity                              Example No.                                                                          Weight                                                                              (ppm)                                                                              ature (°C.)                                                                  (hours)                                                                           --Mw/--Mn                                                                          Point (°C.)                                                                  (cps, at 75° C.)                __________________________________________________________________________    Comparative                                                                          2000  TBT, 10                                                                            170   7-8 2.98 49-50 350                                    Example 1                                                                     Comparative                                                                          2000  "    200   1.5 2.83                                              Example 2                                                                     Comparative                                                                          2000  "    140   14  2.58                                              Example 3                                                                     Example 1                                                                            2000  SnCl.sub.2, 5                                                                      170   5.5 1.76 45-46 204                                    Example 2                                                                            2000  "    140   34.0                                                                              1.61                                              Example 3                                                                            2000  SnCl.sub.2, 20                                                                     140   3   1.54                                              Example 4                                                                            2000  "    130   16  1.55                                              Comparative                                                                          1250  TBT, 10                                                                            170   7-8 2.55 45-47 160                                    Example 4                                                                     Example 5                                                                            1250  SnCl.sub.2, 5                                                                      170   6.5 1.51 37-39  91                                    __________________________________________________________________________     Note                                                                          The melting point was measured by a melting point measuring device Model      MP supplied by Yanagimoto Seisakusho. The viscosity was measured by a         Btype rotary viscometer. The molecular weight distribution --Mw/-- Mn was     determined according to the GPC method.                                  

SYNTHESIS EXAMPLE 6

A four-neck flask equipped with a stirrer, a thermometer, a nitrogenintroducing tube and a condenser was charged with 1938 parts ofε-caprolactone, 62 parts of ethylene glycol and 0.01 part of stannouschloride, and reaction was carried out at 170° C. for 5.5 hours toobtain a polycaprolactone polyol having a hydroxyl value of 56.2 KOHmg/g (the unit will be omitted hereinafter), an acid value of 0.27 KOHmg/g (the unit will be omitted hereinafter), a viscosity of 204 cps at75° C. and a molecular weight distribution of 1.73.

EXAMPLE 7

Physical properties of a polyurethane elastomer prepared by reacting 200parts of the polycaprolactone polyol obtained in Synthesis Example 6which had a molecular distribution of 1.73, with 75 parts of4,4'-diphenylmethane diisocyanate at 80° C. for 1 hour and subjectingthe reaction product to addition polymerization with 12 parts of1,4-butylene glycol as the chain extender, were as follows.

100% Modulus: 40 Kg/cm²

300% Modulus: 90 Kg/cm²

Tensile strength: 392 Kg/cm²

Elongation: 565%

Elastic recovery: 65%

JIS Hardness A: 80

The elastic recovery means the elasticity recovery ratio (20° C.)determined by stretching the sample by 300%, allowing the sample tostand still for 10 minutes from release of stretching and makingcalculation according to the following formula: ##EQU2## in which lstands for the distance between standard lines before stretching and l'stands for the distance between standard lines after stretching andreleasing.

SYNTHESIS EXAMPLE 8

In the same manner as described in Synthesis Example 6, reaction wascarried out at 130° for 16 hours by using 1938 parts of ε-caprolactone,62 parts of ethylene glycol and 0.02 part of stannous chloride to obtaina polycaprolactone polyol having a hydroxyl value of 56.2, an acid valueof 0.20, a viscosity of 151 cps at 75° C. and a molecular weightdistribution of 1.45.

EXAMPLE 9

The polycaprolactone polyol having a molecular weight distribution of1.45, which was obtained in Synthesis Example 8, was reacted in the samemanner according to the same recipe as in Example 7. Physical propertiesof the obtained polyurethane elastomer were as follows.

100% Modulus: 39 Kg/cm²

300% Modulus: 88 Kg/cm²

Tensile strength: 350 Kg/cm²

Elongation: 600%

Elastic recovery: 80%

JIS Hardness A: 79

COMPARATIVE EXAMPLE 5

In the same manner as described in Synthesis Example 6, reaction wascarried out at 170° C. for 6 hours by using 1938 parts ofε-caprolactone, 62 parts of ethylene glycol and 0.02 part of tetrabutyltitanate to obtain a polycaprolactone polyol having a hydroxyl value of52.1, an acid value of 0.21, a viscosity of 350 cps at 75° C. and amolecular weight distribution of 2.98.

The so-obtained polycaprolactone polyol was reacted in the same manneraccording to the same recipe as in Example 7. Physical properties of theobtained polyurethane elastomer were as follows.

100% Modulus: 39 Kg/cm²

300% Modulus: 95 Kg/cm²

Tensile strength: 440 Kg/cm²

Elongation: 550%

Elastic recovery: 40%

JIS Hardness A: 80

COMPARATIVE EXAMPLE 6

In the same manner as described in Synthesis Example 6, reaction wascarried out at 130° C. for 16 hours by using 1938 parts ofε-caprolactone, 62 parts of ethylene glycol and 0.02 part of tetrabutyltitanate to obtain a polycaprolactone polyol having a hydroxyl value of56.2, an acid value of 0.22, a viscosity of 320 cps at 75° C. and amolecular weight distribution of 2.58.

The so-obtained polycaprolactone polyol was reacted in the same manneraccording to the same recipe as in Example 7. Physical properties of theobtained polyurethane elastomer were as follows.

100% Modulus: 40 Kg/cm²

300% Modulus: 93 Kg/cm²

Tensile strength: 430 Kg/cm²

Elongation: 550%

Elastic recovery: 50%

JIS Hardness A: 80

EXAMPLE 10

A 4-neck flask equipped with a stirrer, a thermometer, a droppingfunnel, a nitrogen introducing tube and a condenser was charged with 200parts of the polycaprolactone polyol obtained in Synthesis Example 8,which had a molecular distribution of 1.45, 31.2 parts of neopentylglycol, 101 parts of 4,4'-diphenylmethane diisocyanate and 635 parts ofmethylethyl ketone as the solvent, and 0.7 part of methanol was used asthe reaction stopper. Reaction was conducted at 75° C. for 8 hours toobtain a polyurethane solution having a solid content of 35% and aviscosity of 32,000 cps at 25° C. The polyurethane solution was cast ona glass sheet and dried at 40° C. overnight to obtain a transparentpolyurethane film having the following physical properties.

100% Modulus: 18 Kg/cm²

Tensile strength: 160 Kg/cm²

Elongation: 600%

Elastic recovery: 80%

COMPARATIVE EXAMPLE 7

The polycaprolactone obtained in Comparative Example 5, which had amolecular weight distribution of 2.98, was reacted in the same manneraccording to the same recipe as in Example 10 to obtain a polyurethanesolution having a solid content of 35% and a viscosity of 48,000 at 25°C. A film prepared from this polyurethane solution had the followingphysical properties.

100% Modulus: 18 Kg/cm²

Tensile strength: 170 Kg/cm²

Elongation: 580%

Elastic recovery: 40%

The embodiments of the invention of which an exclusive privilege andproperty is claimed are defined as follows:
 1. A process for thepreparation of polyurethanes which comprises reacting an organicdiisocyanate with a polycaprolactone polyol having a narrow molecularweight distribution in which the ratio of the weight average molecularweight to the number average molecular weight is in the range of from1.1 to 2.0 and the average molecular weight is 500 to 5,000, saidpolycaprolactone polyol having been prepared by subjecting a lactone toring-opening polymerization in the presence of 0.1 to 50 ppm of stannoushalide selected from the group consisting of stannous chloride, stannousbromide and stannous iodide, as a catalyst, and at a temperature of from100° to 230° C.
 2. A process claimed in claim 1 in which said lactone isepsilon-caprolactone.
 3. A polyurethane prepared by the process of claim1.